Automatic winding and cutting apparatus for webs

ABSTRACT

A web winding and cutting apparatus capable of automatically cutting and coiling relatively short lengths of a material in web form onto a core. Excessive damage of the material at the leading edge of the freshly cut web is avoided because the cutting cycle is very short and because a mechanism provides for immediately tightening the web onto the core, so that slipping of the web cannot occur. Cutting is carried out by a mechanism through sudden release of stored energy and optimum tightening of the web onto the core is obtained by controlling the coefficients of friction between the web and the core at one side and between the web and a pressure roller at the other side.

United States Patent [1 1 Smolderen Mar. 18, 1975 AUTOMATIC WINDING ANDCUTTING APPARATUS FOR WEBS [73] Assignee: Agfa-Gevaert, Mortsel, Belgium[22] Filed: Dec. 12, 1973 [21] Appl. No.: 423,980

[30] Foreign Application Priority Data 3,529,785 9/1970 Mistele 242/56 A2/1972 Hellemans 242/56 R l/l974 Byrf 242/56 R Primary Examiner-EdwardJ. McCarthy Attorney, Agent, or Firm-William J. Daniel [57] ABSTRACT Aweb winding and cutting apparatus capable of automatically cutting andcoiling relatively short lengths of a material in web form onto a core.Excessive damage of the material at the leading edge of the freshly cutweb is avoided because the cutting cycle is very short and because amechanism provides for immediately tightening the web onto the core, sothat slipping of the web cannot occur. Cutting is carried out by amechanism through sudden release of stored energy and optimum tighteningof the web onto the core is obtained by controlling the coefficients offriction between the web and the core at one side and between the weband a pressure roller at the other side.

12 Claims, 5 Drawing Figures AUTOMATIC WINDING AND CUTTING APPARATUS FORWEBS The invention is related to a web winding and cutting apparatus andmethod and is particularly concerned with winders and cutters used forcutting a web into predetermined lengths and winding same subsequentlyonto a core in an automatic way.

The invention is particularly well-suited for cutting relatively shortportions of a web of photographic material and winding them subsequentlyonto a core without excessive damage caused by grooves and scratches dueto either mechanical friction between the web and the core or tofluttering of the web around the latter.

The term web denotes any coilable length of sheet material irrespectiveof its width or the material of which it is composed. Thus the inventioncan be used for winding and cutting webs of paper, fabric, highpolymeric material or the like, in already coiled form or as acontinuous web feeding from a web manufacturing plant.

During the manufacture of photographic materials, a web is moved throughcoating and drying stations in succession and wound upon a core in orderto obtain a master-roll. The latter may either be spliced, as it is thecase for motion picture films, or spliced and cut into formats, as isdone for sheet films.

Some photographic material is marketed in rolled lengths of only a fewmeters. The material to be marketed, having already been cut'to thefinal width is wound onto a core by winding apparatus provided with acutting mechanism which cuts the material into the requiredpredetermined lengths for the individual coils. This cutting step iscarried out semior fully automatically and preferably at a relativelyhigh speed.

Present day cutting and winding apparatus generally consist of a devicethat cuts a web transversally be means of a knife and/or a counter-knifeand subse quently guides the freshly cut leading edge of the web towardsa core which may either be provided with an adhesive substance or keptin a certain position promoting an easy pick-up" of the leading edge.Other methods of winding consist in conferring to the core a rotationalspeed corresponding with the feeding speed of the web and subsequentlyguiding the leading edge of the web into a kind of shell which, incombination with an air stream urging the leading edge ofthe web towardsthe core, enables a first part of the web to be rapidly wound onto thecore which is then transferred to a winding station for the winding onthe remainder of the predetermined length of web. When that length hasbeen wound onto the core, the cutting device cuts the web again and thecycle is repeated with a new core, the latter having been brought intostand-by position during the previous winding cycle.

Although the known apparatus is suitable for winding long lengths ofweb, and web which has a very high mechanical strength, the apparatusare not very suitable for winding short lengths of web, particularlywebs or photographic material. A photographic emulsion layer, normally adispersion of silver halide crystals in a gelatinous binder, is veryvulnerable to damage by mechanical friction, and the method of engagingthe leading edge of the web employed in modern winding machines maycause grooves and scratches, at least and especially at the beginning ofa winding cycle since during the winding on of the first convolutionsthe material tend to flutter on the core. Cutting and winding machineswhich use cores provided with adhesives show the inconvenience that mostof the said adhesives are chemical incompatibile with the emulsionlayer. Moreover, some adhesives, called self-sticking, adhere only tosurfaces which are covered with the same adhe' sive and require themachine to be stopped after cutting of the web in order to coat aleading edge of the web and press the coated edge onto the core. Thissupplementary step greatly reduces the operating speed of the machine.Moreover, a part of the web at the beginning of each winding cycle isspoiled and this is unacceptable when relatively short lengths of webare to be wound. In addition the known apparatus is complicated indesign and operation.

It is an aim of the invention to provide a method and a machine in whichthe above mentioned drawbacks are obviated at least to a substantialextent. Another aim is to provide an automatic, high speed windingapparatus for winding short web portions without excessive loss ofmaterial.

The present invention provides a web winding and cutting apparatuscomprising a holder which is adapted to be loaded with empty cores andis movable for bringing said cores successively to a web pick-up andwinding station at which windingon of a least part of a predeterminedlength of web coming from a web supply station takes place. Prior to thecompletion of windingon of such predetermined length of web onto a core,the core holder is displaced to move that core to another position andto bring an empty core into position for receiving the new leading edgeof the supplied web which will be formed when the web length presentlybeing wound onto a core is severed from the following length of web. Webguiding means is provided which moves into operative position inrelation to an empty core after its arrival at the winding station readyfor guiding the new leading edge of the web around the empty core. inaddition, a web severing mechanism is provided which severs thepredetermined length of web from the following length of web at aposition adjacent the pick-up and winding station and while thefollowing part of the web is clamped against the empty core on which itis to be wound. The said severing mechanism is constructed so that theweb severing movement takes place rapidly under energy stored in thesaid mechanism. For example, the mechanism may comprise a compressionspring which bears against an arm carrya ing a web severing knife andwhich is placed in compression by another part of the mechanism prior tothe moment at which the web is to be severed.

According to a preferred feature, the web guiding means comprises ashell which cooperates with an empty core to define a guide passage forthe web, and a web-tightening roller which frictionally engages a webportion as it emerges from said guide passage and tightens the webportion around the core.

The web severing knife may be carried by a first arm and the shell andweb-tightening roller may be carried by a second arm, the two arms beingmounted for approach displacement towards an empty reel at the pickupand winding station, from opposite sides thereof. The second arm mayalso carry a counter-knife so that the web is cut or sheared between theknife and counter-knife.

The invention includes web winding and cutting apparatus comprising:

a. a supply station from which the web to be fed,

b. a turret for supporting at least two cores, the web being wound uponto one of these cores, while the remainder are empty and in stand-byposition:

c. means to confer a predetermined rotational speed to the cores,

d. cutting means for cutting the web after a predetermined length ofsaid web has been wound onto said core, said cutting means comprising aknife mounted on a first arm, which is driven by motor means withapplication of means for accumulating and for suddenly freeing storedenergy, and a counter-knife mounted on a second arm,

e. guide means for guiding the leading edge of the web onto the emptycore, the guide means comprising a guide shell for encircling the emptycore, at least one idler roller capable of rotating against the webbefore, during and after cutting and at least one slippingly dirvenroller for urging the web towards the core after cutting, thecircumferential speed of the slippingly driven roller exceeding thecircumferential speed of said empty core, wherein the coefficient offriction of the material, from which the slippingly driven roller ismade relative to the web is greater than the coefficient of friction ofsaid empty core relative to the web, and

f. means to support the guide means.

The scope of the invention will be exemplified with the help of adescription of a preferred embodiment and with reference to theaccompanying drawings in which:

FIG. 1 is a diagrammatic view of a cutting mechanism embodying theinvention.

FIG. 2 presents the cutting mechanism of FIG. 1, prior to cutting.

FIG. 3 presents the cutting mechanism of FIG. 1, during the cuttingcycle.

FIG. 4 presents the cutting mechanism of FIG. 1, immediately after thecutting cycle.

cut is FIG. 5 is a diagrammatic view of a winding and cut-.

ting apparatus incorporating the invention.'

In FIG. 1 there is shown a cutting mechanism during the winding up stepof a web 1 onto a core 2. The core 2 is positioned on a turret 4, hererepresented by a circle, together with an empty core 3. The turret 4 maybe driven stepwise after each winding cycle in order to bring a new corein winding position.

Around the core 2, being wound up, there is provided a cuttingmechanism, mainly comprising two arms, 5 and 13, both pivotallyjournalled on a shaft 33 on which the cutting and guiding devices forthe web are provided.

On arm 5, which is capable of performing pivotal movement around shaft33 under the influence of airmotor 7, are provided a guide shell 6carrying at its extremity a counterknife 8 and a second air-motor 9which, when energized, extends so as to swing the free end of the arm12, carrying a roller 10 and a guide member 11, towards the guide shell.

On the arm 13, which also pivots around shaft 33 under the action ofair-motor 19, are provided the knife 17 and the rollers 16 and 18,roller 16 being separately mounted on the arm 14 and elasticallysupported by means ofa spring 15. Between the air-motor l9 and the arm13, there is provided a dash-pot 35 in which two springs, 20 and 21, arehoused with their mutually adjacent ends bearing against the piston 36at the end of the piston rod of air-motor 19. Arm 13 carries anextension crank 25 at its extremity which, upon rotation contacts a pawl26, which is able to move longitudinally under action of air-motor 27.The arm 13 is also provided at its pivoted end with teeth 24, whichafter a certain pivotal motion of the arms 13 about shaft 33 engage withthe toothed end of lever 23, which is pivotally connected to the arm ofair-motor 22.

FIG. 2 presents the cutting mechanism in standby position, immediatelybefore the cutting cycle. The core 2, having nearly attained its finaldiameter has moved over whereas the empty core 3 which is slippinglydriven by a motor (not shown) is placed between the arms 5 and 13, byhalf a revolution of the turret 4 and starts rotating so that itscircumferential speed is equalto the speed of the moving web. Arm 5 hasalready reached its position for cutting and the guide shell 6 lies inclose proximity to the empty core 3. At the same time, air-motor 9 urgesroller 10 against the empty core 3, so that the latter becomessurrrounded over about three quarters of its circumfer ence. Incontrast, arm 13 is temporarily maintained in stand-by position, due tothe fact that upon its rotation about shaft 33, its movement is arrestedat a given moment because the extension crank 25 is stopped by pawl 26.The arrestment of arm 13, while air-motor 19 remains energized, causesspring 20 to be compressed, whereas spring 21 is completely released.

In FIG. 3 is shown the cutting cycle, once a sufficient amount of webhas been wound upon the core 2. At that moment the extension crank 25 isreleased by the pawl 26 due to retraction of the piston of air motor 27,and the energy, accumulated in the spring 20 is suddenly freed, so thatarm 13 is rapidly swung further upwardly by the expansion of spring 20(which has a greater compliance than that of spring 21) so that theknife 17 is driven through the web. At the same time the roller 16resiliently presses the web 1 against the core 3 immediately behind theline of the cut.

The roller 18 provided at the end of arm 13 trailing cutoff end of theweb as it travels towards the core 2, so avoiding an occasionalfluttering of that end against machine parts. In the mean time, spring21 has become compressed, whereas spring 20 is released. The whole cycleis carried out in a few hundredths of a second.

In FIG. 4 the situation immediately after the cutting stage isillustrated. At the moment air-motor 22 is energized and causes thetoothed end of lever 23 to interlock with the teeth 24 on arm 13. Inthis way the arm 13 is maintained in a projected position, guaranteeingoptimum contact between the web and the rollers while occasionalvibrations of the arm are completely prevented. The knife 17 has alreadybeen withdrawn, but by the expansion of the spring 15 roller 16 remainsin biased position against the core 3.

The leading edge of the web is guided in the space defined by the guideshell 6 and the core 3. By the fact that frictional contact occurs firstbetween the web 1 and the roller 16 just prior to cutting and that atthe instant of cutting, roller 16, web 1 and core 3 are firmly urgedtoward each other under influence of spring 15 which becomes compressed,the web 1 further advances in the space formed by the guide shell andthe core. Because no difference in speed between the web 1 and the core3 exists, the leading end of web 1 may flutter during the period that itadvances from the knife upto roller 10, as no tightening action occurs.

Roller is slippingly driven in such a way that when not contacting core3 its circumferential speed is higher than that of the core 3. Roller 10consists of or is provided with a layer of a material which has a higherfrictional coefficient with the web material than does the core 3.Preferably the roller 10 is made of or coated with rubber. When the webreaches roller 10, the portion of the web contacted by the rolleracquires a speed equal to the circumferential speed of said roller 10,so that the web 1 temporarily slides relative to the core 3 and the webbecomes tightened. Then the leading edge is gripped between thefollowing part of the web 1 and the core 3 and a new winding cycle canstart.

Once a few windings are wound onto the core 3, the airmotors 7 and 19are de-energized and the arms 5 and 13 return to their inital position.The whole cycle is repeated when a predetermined amount of web is woundonto the core.

FIG. 5 gives a diagrammatic view of a complete winding apparatusembodying the invention. From a supply roller 29, web 1 is fed to a core2 by passing over guide rollers 30, a tension regulating device,consisting of a weight 32 and a dancer-roller 31, and the cutting deviceformed by the arms 5 and 13. A number of empty cores 39, lying on aninclined plane 40, are prepared to be fed to a cradle 4-1, mounted atthe extremity of the arm of air-motor 37. A turret 38, provided at itsextremity with a fork 42, carries an empty roller to turret 4 whenair-motor 37 becomes energized. The other extremity of turret 38 may beprovided with a member suited to receive finished rollers, which may beforwarded to a packing station (not shown) for example.

The operation of the device is as follows (FIG. 5). The web 1 is woundonto core 2 which is in operating position. Once a predetermined lengthof web is wound onto the core, which may easily be detected by meansknown in the art, the turret 4 starts revolving over a given angle inthis case 180 in order to bring empty core 3 in operating position.

When the core 2 (now in the position at left of turret 4) has almostfully wound up the amount of web which was preliminarily defined, theair motors 7 and 19 are energized and core 3, being slippingly driven,starts rotating at a circumferential speed, equal to the linear speed ofthe web 1.

The presence of the extension crank 25 urging against pawl 26 limits themovement of the arm 13, attached to air motor 19, but by the continuousenergizing of the latter, spring 20, enclosed in dash pot 35 becomescompressed, whereas spring 21, also enclosed in dash pot 35 isstretched.

Arm 5, carrying guide shell 6 at its free extremity which encircles theempty core 3, carries also another air motor 9, which by means of alever 12 pivotally secured to arm 5, urges roller 10 aganist core 3.Roller 10 is slippingly driven and attains the same circumferentialspeed as that of core 3. When, however, roller 10 is free turning andout of contact with core 3, its circumferential speed exceeds that ofcore 3.

The cutting cycle itself, is started when air motor 27 becomes energizedand retracts pawl 26, freeing extension crank 25. This causes spring 20,which has a greater compliance than spring 21, to expand suddenly and tolift arm 13 somewhat further driving knife 17 through the web to be cutby a short, single stroke. In

10 jected position, air motor 22 is energized causing the toothed end 23at its associated lever to engage the teeth 24 latching thereby the arm13 in that position and at the same time to preventing possibleoscillation of the latter.

The web 1 continues to advance at its normal speed because it is pressedbetween roller 16 and core 3, the

. latter being driven at the speed of the web. So, the leading edge isfurther advanced in the shallow passage formed by the guide shell 6 andthe core 3, until it reaches roller 10. Then, the web movement isaccelerated on account of the fact that this roller is of rotating at ahigher circumferential speed of the web 1 and because the coefficient offriction between roller 10 and the web is greater than the coefficientof friction between core 3 and the web. Hence possible fluttering of theweb around the core 3 is automatically neturalized and the web istightened around the core. With the help of the supplementary guidemember 11 the leading end of the web is directed between the web and thecore, so that the step of winding the web on core 3 is startedautomatically.

After a few windings are round on core 3, the air motor 22 is energizedin such a. way that its piston moves in an opposite direction, freeingthe toothed end. The same cycle is performed with air motor 9, causingroller 10 to come out of contact with the web. Then the main air motors7 and 19 return arms 5 and 13 to their starting positions, so that core3 is no longer surrounded by guide shell 6 and the rollers 10 and 16.-The partial rotation of arm 13 swings the extension crank 25 past thepawl 26, the air motor 27 becomes then energized so that the latterpushes said pawl in forward direction.

The roll 2, still being on the turret is removed theefrom by a kind ofcradle mounted on one extremity of a turret 38 which forwards the rollto a receiving station (not shown). In the same time a fork 42 forces acore 39 into stand-by position with the help of a cradle 41 actuated bya vertically operating air motor 37. The features explained in thisparagraph however are not part of the invention.

From the foregoing it may be concluded that new automatic winding andcutting apparatus is provided which is suited for many purpose.

The utilization of the sudden freeing of accumulated energy combinedwith the use of mechanical parts of low weight enables a quick and cleancutting of the web. In a preferred embodiment, the time required to cutthe web and winding one turn amounts only to about one-tenth of asecond.

The apparatus may be completed with counting circuits, measuring andregulatingdevices and alarm circuits, without however departing from thescope and spirit of the invention. Also pneumatic deivces may bereplaced by either their electrical or electromechanical equivalents.The appratus may operate individually or as an end station of aproduction process and may be adapted for very small as for very bigrollers as well.

Therefore, the foregoing apparatus is merely described as an example,and the scope and spirit of the invention shall be derived from theappended claims.

We claim:

1. A web winding and cutting apparatus for converting a continuouslytravelling web into rolls, said winding apparatus comprising:

a. a supply station from which the web to be cut is fed,

b. a turret for supporting at least two cores, said web being wound uponto one of these cores, with the remainder empty and in stand-byposition,

c. means for rotatably driving the respective cores at a predeterminedrotational speed,

d. cutting means for cutting said web after a predetermined length ofsaid web has been wound onto said core, said cutting means comprising aknife mounted on a first arm, means for biasing said arm to cuttingposition, releasable detent means restraining the arm from moving tosaid cutting position and energy storage means between said biasingmeans and said arm to store the biasing force of said biasinng meansuntil said detent means is released,

e. guide means for guiding the leading edge of said cut web onto saidempty core, said guide means comprising a guide shell for encirclingsaid empty core, at least one idler roller capable of rotating againstthe web adjacent said knife during cutting and at least one slippinglydriven roller downstream of said guide shell for tightening the webagainst the core after cutting, said slippingly driven roller beingdriven at a circumferential speed exceeding the circumferintial speed ofsaid empty core and having a coefficient of friction relative to the webgreater than the coefficient of friction of said empty core relative tothe web, and

f. means to support said guide means.

2. A web winding and cutting apparatus according to claim 1 in whichsaid idler roller is mounted on said first arm, and said guide shell andsaid slippingly driven roller are mounted on a second arm arrangedgenerally on the opposite side of said core from said first arm.

3. A web winding and cutting apparatus according to claim 1 in whichsaid energy storage means comprise a pair of springs, one of which iscompressed and the other released under action of said arm biasing meanswhen the arm is restrained against movement.

4. A web winding and cutting apparatus, according to claim 3, in whichsaid first spring has a greater compliance than said second spring.

5. A web winding and cutting apparatus, according to claim 1, in whichsaid guide shell encircles the empty core over at least 6. A web windingand cutting apparatus, according to claim 1, in which the surfacematerial of the slippingly driven roller is rubber.

7. A web winding and cutting apparatus, according to claim 1 which isprovided with stabilizing means in to keep the guide means in a stableposition immediately after the cutting.

8. A web winding and cutting apparatus according to claim 1 in whichsaid dentent means comprises an extension crank integral with said firstarm, and a retractable latching pawl cooperating with said crank.

9. A web winding and cutting apparatus according to claim 8 includingmeans for retracting and projecting said pawl.

10. A web winding and cutting apparatus according to claim 7 in whichsaid stabilizing means consist of an array of ratchet teeth movablebodily with said guide means and a pawl interlocking with said array.

11. In a method of winding a continuously travelling web into rolls oncores by the steps of delivering the web to a first core in activewinding position along a fixed path at a predetermined speed,positioning an empty core in stand-by position adjacent said web pathupstream of said actively winding core while rotating the empty core ata speed substantially equal to the web speed, severing said web with aknife blade at a locus adjacent said second core and guiding the leadingedge of the severed web onto said empty core to initiate windingthereon, the improvement of resiliently biasing said knife toward aposition cutting said web while restraining said knife against movementto said cutting position until resilient energy is accummulated, andreleasing said knife from restraint whereby said knife is impelled tocutting position by said accummulated resilient energy.

12. In a method of winding a continuously travelling web into rolls oncores by the steps of delivering the web to a first core in activewinding position along a fixed path at a predetermined speed,positioning an empty core in stand-by position adjacent said web pathupstream of said actively winding core while rotating the empty core ata speed substantially equal to the web speed, severing said web with aknife blade at a locus adjacent said second core and guiding the leadingedge of the severed web through an arcuate passageway extending throughan arc of at least 180 around said empty core, the improvement ofadjacent the downstream end of said passageway frictionally engaging theleading web end to advance the sameat a linear speed exceeding thelinear speed of said core in order to tighten the web end around saidempty core.

UNITED STATES PATENT OFFEQE CERTIFICATE OF GO.EQTEN PATENT NO. 3,871,595DATED March 18 1975 |NVENTOR(S) I Albert Emiel SMOLDE REN It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column '7, line 25, delete "biasinng" and insert --biasingline 35,delete circumferintial" and insert --circumferential Column 8, line 7, 4delete "which is provided with" and insert --inc luding and also in thesame line delete'"in" Signed and sealed this 20th day of May 1975,

(SEAL) Attest:

Co MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer1 r and Trademarks

1. A web winding and cutting apparatus for converting a continuouslytravelling web into rolls, said winding apparatus comprising: a. asupply station from which the web to be cut is fed, b. a turret forsupporting at least two cores, said web being wound up onto one of thesecores, with the remainder empty and in stand-by position, c. means forrotatably driving the respective cores at a predetermined rotationalspeed, d. cutting means for cutting said web after a predeterminedlength of said web has been wound onto said core, said cutting meanscomprising a knife mounted on a first arm, means for biasing said arm tocutting position, releasable detent means restraining the arm frommoving to said cutting position and energy storage means between saidbiasing means and said arm to store the biasing force of said biasinngmeans until said detent means is released, e. guide means for guidingthe leading edge of said cut web onto said empty core, said guide meanscomprising a guide shell for encircling said empty core, at least oneidler roller capable of rotating against the web adjacent said knifeduring cutting and at least one slippingly driven roller downstream ofsaid guide shell for tightening the web against the core after cutting,said slippingly driven roller being driven at a circumferential speedexceeding the circumferintial speed of said empty core and having acoefficient of friction relative to the web greater than the coefficientof friction of said empty core relative to the web, and f. means tosupport said guide means.
 2. A web winding and cutting apparatusaccording to claim 1 in which said idler roller is mounted on said firstarm, and said guide shell and said slippingly driven roller are mountedon a second arm arranged generally on the opposite side of said corefrom said first arm.
 3. A web winding and cutting apparatus according toclaim 1 in which said energy storage means comprise a pair of springs,one of which is compressed and the other released under action of saidarm biasing means when the arm is restrained against Movement.
 4. A webwinding and cutting apparatus, according to claim 3, in which said firstspring has a greater compliance than said second spring.
 5. A webwinding and cutting apparatus, according to claim 1, in which said guideshell encircles the empty core over at least 180*.
 6. A web winding andcutting apparatus, according to claim 1, in which the surface materialof the slippingly driven roller is rubber.
 7. A web winding and cuttingapparatus, according to claim 1 which is provided with stabilizing meansin to keep the guide means in a stable position immediately after thecutting.
 8. A web winding and cutting apparatus according to claim 1 inwhich said dentent means comprises an extension crank integral with saidfirst arm, and a retractable latching pawl cooperating with said crank.9. A web winding and cutting apparatus according to claim 8 includingmeans for retracting and projecting said pawl.
 10. A web winding andcutting apparatus according to claim 7 in which said stabilizing meansconsist of an array of ratchet teeth movable bodily with said guidemeans and a pawl interlocking with said array.
 11. In a method ofwinding a continuously travelling web into rolls on cores by the stepsof delivering the web to a first core in active winding position along afixed path at a predetermined speed, positioning an empty core instand-by position adjacent said web path upstream of said activelywinding core while rotating the empty core at a speed substantiallyequal to the web speed, severing said web with a knife blade at a locusadjacent said second core and guiding the leading edge of the severedweb onto said empty core to initiate winding thereon, the improvement ofresiliently biasing said knife toward a position cutting said web whilerestraining said knife against movement to said cutting position untilresilient energy is accummulated, and releasing said knife fromrestraint whereby said knife is impelled to cutting position by saidaccummulated resilient energy.
 12. In a method of winding a continuouslytravelling web into rolls on cores by the steps of delivering the web toa first core in active winding position along a fixed path at apredetermined speed, positioning an empty core in stand-by positionadjacent said web path upstream of said actively winding core whilerotating the empty core at a speed substantially equal to the web speed,severing said web with a knife blade at a locus adjacent said secondcore and guiding the leading edge of the severed web through an arcuatepassageway extending through an arc of at least 180* around said emptycore, the improvement of adjacent the downstream end of said passagewayfrictionally engaging the leading web end to advance the same at alinear speed exceeding the linear speed of said core in order to tightenthe web end around said empty core.